Electric control means for automatic conveyer systems



K. H. QUAIL 2,688,934

ELECTRIC CONTROL MEANS RoR AUTOMATIC CoNvEYER sYsTEMs 9 Sheet's-Sheet 1Sept. 14, 1954 Filed Nov. 8, 1945 HTraF/VEYS.

K. H. QUAIL Sept. 14, 1954 ELECTRIC CONTROL MEANS FOR AUTOMATIC CONVEYERSYSTEMS Filed Nov. 8, 1945 9 Sheets-Sheet 2 sa gz /ao I N V EN TORHr///YEXS,

K. H. QUAIL sept. 14, 1954 Filed Nov. 8, 1945 9 Sheets-Sheet 3 l UMS m w5 5J .w c y,

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K. H. QUAIL sept. 14, 1954 9 Sheets-Sheet 4 Filed Nov. 8, 1945 ma F TQma T@ 4 WQ c M (j T z 71M n n Z n a M H ,W m. i n y 4e .z Hm E .1; ,M,anw @L/ E m E@ We e J ,r M mm il ma o 7 7 a r Ww y 51M@ L .2 W n:4 h wn z T. M M W i@ w j; m Si r M 1L K. H. QUAIL Sept. 14, 1954 ELECTRICCONTROL MEANS FOR AUTOMATIC CONVEYER SYSTEMS Filed NOV. 8, 1945 9Sheets-Sheet 5 Sept. 14, 1954 ELECTRIC Filed Nov. 8, 1945 K. H. QUAIL2,688,934 CONTROL MEANS TOR AUTOMATIC cONvEYER sYsTEMs 9 Sheets-Sheet 6Sept. 14, 1954 K H, QUA|L 2,688,934

ELECTRIC CONTROL MEANS FOR AUTOMATIC CONVEYER SYSTEMS Filed Nov. 8, 19459 Sheets-Sheet '7 Sept. 14, 1954 K. H. QuAlL 2,688,934

ELECTRIC CONTROL MEANS FOR AUTOMATIC CONVEYER SYSTEMS Filed NOV. 8, 19459 Sheets-Sheet 8 Sept. 14, 1954 K. H. QUA". 2,688,934

ELECTRIC CONTROL MEANs EOE AUTOMATIC CONVEYER sysTEMs Filed NOV. 8, 19459 Sheets-Sheet 9 A7770/V/VEV5,

Patented Sept. 14, 1954 ,V smfrss Param" orner;

ELECTRICEONTROL MEANS FORAAUTO- l MATLIC ,-CONVEYER SYSTEMS KennethHf'Qual, Pleasant Ridge, Mich., vasfslgnon -by 4rnesne assignments, toMechanical Handling Systems, yinc., Detroit, Mich., ra fooi lporation oflMichigan Applica-tion Noverrbr 8, 194'5, -Serial N0."627,462

l i l'11] Ulanfs.

miie present invention 'relates `to automatica'lly controlledfd'espatcriin'g systems land is more '-particularly directed to theprovision of improved electrical control arrangements ffor use iiniconnection with such-systems.

(Cl. 11M-388) 2 to 'avoid vlint-errerenee between the respective-fcarri'ers A-at fthe var-'ions track Vlswitches for elsewhere upon thesystem. "So 'farvas the present applicant is aware, 3no systems lhaveFheretofore been `pro- 5vidediWliioh-satisifactorilymeetfthetoregoingigenmt "will be appreciatedfrom a jcomplete underorally statedrequirements.- standing of thelpres'ent invention, that, in a Wilththe ioregoingconsiderations iinvliewacgenenijcsense, the improvements thereof are apicordi-ngly,principal obects of ithepresentinvenplioaio-letoawide vai'rietylof'systemswhich ein tion are lto provide an lautoma'iically -controlledinstrumentality is required to -be despatched @to 1'@ despatehing:system -generieally, lmay b'e any :of a variety oi :positions along:any 'of a characterized ason'einany-onefdf alp'luvariety ofdifferentrpaths or routes. Examples ralitymf Jinstrument'aliti'esoperating-alongasysofrsuoh systems, in the ycarrier field, includesurtem for :routes may :be dispatched :tromany.desfac'erailways,:overheadrailwaysnand the like. tination thereon toany other destination; 'Ito ai the present time, e @referred applicationof provide such la system for track :guided carriers,

the invention 'eis connection with overhead monorail systems of thesgener'al type which, in recent years, :have @been 'fused fto A:anincreasingly large '.'extent yin facto'ries ft'o 'handle lthedistribution 'of materials and 'products 5'as .an incident a'tomanufacturing, storage, andsliipping foperation's. By way fofillustration, 4-bult not of limitation-accordingly, the invention is 'sodisclosed herein.

f .It'wirlfbeniiderstoodthat overhead carrliersystems of 'the aboveindicated ltype .may 1Icomprise a wide Variety of tra'ck Vor monorail:arrangements. Usually, Yoi course, such monorail :systems involve :a`4main lin'e 'zand a plurality fof branch lines or sidings, which :areconnected "to thel main line fby way 'of `siding :switches and vexitswitches. inestinations'or fst'opping points may '-be variouslydistributed round the fmonorail system, being usuallyllocated onthesidings,VA so 'as t'o permit 'unobstructed 'travel l'of carriers on thelmain where-in individual carriers, 'so dispatched, .fare

' caused -to :operate :such track :switches :as are necessary Ito enableithem to yenter fthe 4siding or sidings corresponding to the desired`lastima-- tion; =toiproviele :such systems Ewherein:eachftrack switchand each destination .is provided with electrical :apparatus which,under :appropriate conditions, mesponds `:to :the 4zaimgiroach -ro acarrier to cause that carrier to :actuate .a particular switch-:orto.befstopped oriotherwise controilei lat a particular `destinaii'on; toprovide :such :systems wherein each icanrni'eris providedWithipresettable lelectrical :contro-l apparatus, carried themen, whichis :arranged to ylue :automatically coupled to the@electrical-'apparatus at Vtherespectime track switches fand :at theYdestinations, :so ias toxpfrovid'e the faforesaidoontroktoaprovidefsnch systems wherein the :apparatus .on each carrier-lsarranged to be energized, iin accordance' With-any line. im'divi'dualsidings-may be provided with 3 offfalpmmmy of-,diiiferent .eleemcmconditions, one or imore'rde'stinations Vdistrlc'utfed along the '3corresponding :respectively to the selected laesengththel'ftinat'ron,sind wherein the fcontrol .apparatus at fForfa number of years there hasbeen -a decided need tor a simple, 'economically `manufactured andinstalled control system, :for #carrier systems of *the aboveF-type,which incorporates means whereby-'any one of ia plurality Vlo'fcarriers, operable V:upon the system, can be dispatched from anydestination on Sthe system, to any other destinationfon th'e system, thearrangement 'being such that in trayelling'from'the dispatching pointto'lthe desti-natiomfthe dispatched ycarrier may be Caused toVaiutornatically voperate such 'track switchesvals Aare needed to directit'to the siding on mhich'the destinationfis located, and the`a'rrangement 'ibeing 'further such that rindividual carriers may,-un'd'er appropriate conditions, be controlled by 'carriers'ahea'd of'them Jon the systern, so as to avo'iddirecting a carrier to a sidingwhich islnot in 'condition *to receive mand seas the variousyswitchestand :at .the various destinations fare'sselectvely responsive,:to such-:different electrical conditions; "to y.provide fsuch systemsywherein, independently of fthe-:numberfof destina;- ti'on's and the:number fof track switches whichzare to be operated Cbya particularcanrierachfcarrier requires only a pairiof oontrollfcurrentf collectors,Wiierein'rfnrther the only control connectons'extending between :therespective fdestinationsfis a single sectionalized control lbusrwhich,along with the y:usual `,power lbuscs,A may 'heisa-tried idirectly by'the 'overhead track `.orim'cmorail; land toppro- Vde such systemsembodying improved Vmeans for `'prev-'entinfg interference betweensuccessive carriers Jon' fthe main tline l for on :sidinga l 'and toprever-it *the er'rtranoe fof #carriers on tito sldin'gs which-are 'notf iin 4shape 1' to receive' them.

"With the above asf-Wellesfoftherandin-certain cases, more detailedobjects in view, preferred but illustrative embodiments of the inventionare shown in the accompanying drawings, throughout the several views ofwhich corresponding reference characters are used to designatecorresponding parts and in which:`

Figure 1 is a diagrammatic layout of an automatically controlledoverhead monorail system embodying the invention; Figure 2 is a view inside elevation of a tractor unit with which each carrier, operating uponthe system of Figure 1, may be provided; i i

Figure 3 is a view in front elevation, of the tractor unit of Figure 2;

Figure 4 is a view in perspective of a conventional track switchconstruction, which may be utilized in connection with both the sidingswitches and the exit switches, which switches are diagrarmnaticallyshown in Figures 1, 5A, 5B, and 5C, 6 and 8;

Figures 5A, 5B, and 5C, collectively, diagrammatically illustrate, withreference to the system of Fig. 1, the control apparatus that isprovided at certain of the siding switches, the control apparatus thatis provided at each destination, the control apparatus that is providedat each exit, and the control apparatus which is preferably provided oneach carrier in the system. In reading Figures 5A, 5B, and 5C, the sheetcontaining Figure 5B may be placed immediately to the right of the sheetcontaining Figure 5A, and the sheet containing Figure 5C, arrangedendwise, should be placed immediately to the right of the sheetcontaining Figure 5B;

Figure 6l is a diagrammatic view of the control apparatus which, for asystem as shown in Fig. 1, is provided at each siding switch, other thanthe siding ,switches which are arranged as shown in Figure 5A;

Figure 7 is an outline view of a slightly modied monorail of tracksystem;

f Figure 8 is a diagrammatic view of control apparatus which may beprovided at certain of the siding switches of Figure 7; f

vFigure 9 is a schedule of the operating characteristics of the variouslimit switches which are operated by the track switches;

Figures 10A, 10B, and 10C, collectively, diagrammatically illustrate amodification of the invention, the control apparatus provided at eachsiding switch being shown in Fig. 10A, the control apparatus that' isprovided yon each carrier being shown in Fig. 10B, and the controlapparatus that is provided at each exit switch being shown in Fig. 10C.Additionally, Fig. 10C illustrates the control apparatus that isprovided at each destination, and also illustrates auxiliary controlapparatus which may be distributed throughout the system to maintain adesired spacing between carriers. If, in reading Figs. 10A, 10B, and10C, the sheet containing Fig. 10B is .placed immediately to the rightand aligned with the sheet containing Fig. 10A, and the sheet containingFig. 10C is placed to the right and somewhat higher than the Vsheetcontaining Fig. 10B, the three sheets collectively illustrate twosections of main line which are interconnected by a siding; and` Figure11 is an outline view of a track layout to which vthe system of Figures10A, 10B, and 10C is applicable.

Referring rst to the embodiment of Figures l through 6, the illustrativemonorail or track system (Figure l) `comprises an ovehead track, themain track R whereof is arranged in a continuous loop. The tracksystemalso comprises aplurality of sidings RI, R2, R3, R4, R5, and R6.AS illustrated, siding Rl contains only a single destination lA-IB, andas an example, such siding may be used as a loading or storage zone, onwhich a plurality of carriers may be positioned. The destination IA-IBmight, for Vexample-serve as a principal dispatching station.

The siding R2 is illustrated as conta' ing a plurality of successivedestinations 2A--IB through 2A|0B, the character 2A indicating thesecond siding; and the characters IB, 2B, etc., indicating the positionof the respective destinations along the siding.

The sidings R3 and R4 are interconnected by a series of sidings (RM-R35)each having only a single destination individual thereto, saiddestinations being designated 3A-IB through 3A--|0B. As before, thedestination characters 3A indicate that the destination is one whichmust be reached by entering siding R3, whereas the charactersi IAB,etc., correspond to the individual subordinate sidings and thedestinations thereon.

Sidings R5 and R6 are interconnected byl a plurality of subordinatesidings', each also containing only a single destination; f

As is indicated by the dotted lines 20 as many additional sidings as maybe desired may be associated with the main track R, a feature of thepresent system being that a virtually unlimited number of sidings andstations may be provided without any material alteration in the controlsystem.

A siding switch is provided at the junction between the entering end ofeach main or subordinate siding and the track from which it branches andsuch siding switches and their associated controllers are designated SSand SS. Similarly, an exit switch is provided at the outgoing end ofeach siding in the system, all such exit switches and their associatedcontrollers being identical and being designated ES.

The monorail may, of course, be variously con structed, and isillustrated in Figures 3 through 6 as being of usual T section. Aplurality of spaced hangers serve to support the main monorail or trackR. structurally, the individual siding and exit switches may be ofconventional construction, the difference between the controllerstherefor being described below;`

' As appears most clearly in Figure LLeach switchk may comprise a pairof rail sections 26 and 26,

which are supported upon a motor driven slide' 23. The slide 28 for eachsiding switch is adapted to be moved betweenlits two operative positionsby a motor SM (Figurev 4) `and .the slide 28,forming part of each` exitswitch is, adapted to be moved between its two positions byV means of amotor EM. Further in accordance with conventional practice, each switchstructure may be provided witha plurality of limit switches (not shownin Figure 4) which aremechanicallyoperated by the movements thereof.Theselimit switches are shown in Figures 5A, 5C, 6 and- 8 and arediscussed further below. .l v g Theindividual carriers may, of course,be variously constructed depending upon thematerial to be handledthereby.` As previouslyv stated, these carriers are preferably of theelectrically selfpropelled type. Suchvcarriers conventionally include atractor unit and an illustrationv of such a unit is shown in Figures 2and 3. In these gures, the tractor is supported upon the main rail R, bymeans of spaced pairs of railwheels 3 0, which supportingly engage theange of the' associated monorail or track. Each tractor furthercomprises a .driving :motor designated TM Elig-- ures 2,13, and 5B. Thedriving connection :between each motor TlVl-.and :the rail, in the .con-Venztional type illustrated, .comprises .a pneumatic tired tractionwheel 32, which trictionally fengages the underside of .the track. Eachtractor Iunit :is also provided with a plurality of .supporting members.'54, :from which the .particular y.carriage yor body structure,associated with the ztra'ctor, may be suspended. Each tractor jmay :alsocarry the :carrier mounted control'elements `which are shown fin Figure5B, and, zfor this purpose, vmay be 'provided vwith .a ,control cabinet.36. In accordance lwith'thepresent invention, a push ibuttonstation 38:may 'be exibly supported from the cabinet 3.6, vand 'the station 38,may, and 1preferably idees, carry the manually operable .controlswitcheswhichare needed to make a destination selection and to controlthe starting of the individual tractor unit.

As illustrated, 'each tractor motor TM, is supplied Vwith power, through`usual spring biased current collectors 40 andf42, from .bus .bars XandY which are carried by the previously mentioned hangers 22. Bus .bars Xand Y may hesupplied with alternating current from any suitable sourcenot shown, and 'it will be understood, of course, that if desired,multiphase `arrangements may be used instead of the indicated singlephase arrangement.

As is indicated. diagrammatically in Figure 1, and in greater detail inFigures 5A, 5B, and 5C, the bus bars .X and Y may Vand preferably do eX-tend continuously along the monorail system. In the indicated system,bus .bar Y is utilized as the return line, and all runs of this bus bar,on sidings and on ,the main track may be and :preferably areelectrically continuous. This continuity may loe-effected by providingflexible jumpers at the various .switch points as will be appreciated.All "runs of fthe supply bus X are also preferably electricallycontinuous, 4with the exception that,` as shown in Figure 5B, the bux Xis sectionalized in the region of each destination, all yas described inYmore .detail below.

.An important feature of the present yinvention resides in the fact thatonly a single control bus .b ar .or conductor C' is required. As shownin Figure .3, lthe bus .bar C is also carried'by the hangers 22 and isdisposed to be electrically engaged by a pair of longitudinally spacedcurrent collectors LC and TC, the collector LC being hereinafterreferred to as the leading control collector, and the collector 'TCbeing hereinafter referred to as the trailing control collector. Thelongitudinal spacing between the power collectors 4U and 42 `ispreferably substantially less than the spacing between the controlcollectors LC and TC.

.Moreoven the `longitudinal spacing between the control collectors ispreferably somewhat in excess lof the overall length of the carrier.

. Preferably, l.the control bus C is sectionalized throughout itslength. The sectionalizing at sidngswitches, exit switches and atdestinations is shown in detail in Figs. 5A, 5B, 5C, 6 and 8, inwhichfigures the control bus sections yare given .the referencecharacter C followed by asubscript number. -Elsewhere than at switchesand destinations, it is preferred that the control bus C he divided intoa plurality of sections, each slightlyshorter than the spacingbetween'the control collectors LC and TC. All such short sectionalwhichare diagrammatically shown in Fig. 1,2.hearthe reference character C.

.Referring to Figure 35A, the -sectionalizing .of the 1,

6K, control lbus in .the Aregion .of reach-.siding .switch SS :isrsuchas .to .denne a plurality 'of' `bus bar sections CSI through CTI.fPreferably1but1=not necessarily, Vthe .spacing .between .the ends ofadjacent' sections 'CI VAthrough CTI, as well as `the hereinafterdescribed sections, is somewhat iiless than the "lengthnfweach controlcollector LC and TC. As shown, `sections :C6 .and'C'I are jumperedtogether, it being .understood-that .each .section CJ is :carried Lby:and moves l:with the vcorrespending switch Also :adjacent reach sidingswitch, the control bus C which extends Aalong the "correspondingsiding, iis interruptedto'dene .the three sections G8, C9, '.and yClsll,.section C8 .fbeing carried by the :corresponding switch SS, and beingjumpered to the previously mentioned .switch-.CFL

' .As .appears in Figure 5B, aswell as in .the 'lefthand :portion :ofFigure l5C,..the control .bus :C is also interrupted .in the immediatelregion :of each destinationto define fa short stop control sec tionvC=:II. Eachk stop control section is pref-` erably :preceded `by -arelatively long :section C412.,

the length whereof is determineduby the distano inadvanceof adestination, at which ya carrier .is stopped, it 'is :desired to hold afollowing carrier.

. In the :illustrated case, Fig. 5B, the Ydestination AZ-:IBis..relatively1near the associate-d `siding switch, Consequently,section CIZ extends to section ,C t0, asrseen in Fig. 5A.

Figures 5A, 15B, and 5C specically 4show two destinations, '2A-JB, and2li-2B, -being respectively the first .and second destinations-zon thesecond .siding R2 (Figure l). Depending upon the .distance between such.destinations lthe section CI I for the iirst destination and the.section CI 2 for the second destination, may be separated 'by .one or`a series of intervening sections C, :two :beingshown in Fig. :5B Similarcornments apply vto the sectionalizing between lthe remainingdestinations cna particularsiding. Also depending upon the spacingbetween the last destination on a particular siding and its :exitswitch, :one or 'more vsections .C `may .intervene between the sectionCI I for such last destination and the nrst control `section C20associated with such switch.

`In the Vregion of each exit switch, the Amain track portion of thecontrol bus bar C` is interrupted to denne` the sections CIS, CIB, CII,and `CI8, and the siding portion of the control bus bar is sectionalizedto define the sections C20, and C2I, it being recognized that bus barsections C16 and C2I are carried by and are moved by the correspondingexit switch ES.

In the description of operation, mention -is made of those 'instances inwhich it is important that Va particular bus bar section CI-C2-etc. havea particular length, and, though diagrammatic, the indicated lengths ofthe bus bar sections, -in Figures 5A, 5B, and 5C are approximately toscale with respect to the indicated spacings between the control andpower collectors, carried .by the carrier. Unless otherwise stated, itmay ,be assumed that the length of each bus bar section is somewhat lessthan the LC' and TC spacing so that such collectors do notsimultaneously engage the .same section; and thatthe collectors LC andTC are long enough to bridge the gaps between successive sections.

The Lcontrol apparatus for each siding andfexit switch may be andpreferably is located Aat lor near suchswitch. Such apparatus for eachsidi ing .switch SS, shown in Fig. 5A, comprises, in addition 4to the'`driving motor ySM therefor, a

` schedule given below.

SRS, all of which may be of conventional electro- `magnetically operatedconstruction, the contacts whereof bear corresponding referencecharacters with the subscripts a, b, c, etc. These contacts occupy theillustrated positions when the corresponding coils are de-energized, andoccupy opposite positions when and so long as the corresponding sidingswitch SS, and occupy the closed and open positions under the conditionsand at the times specified in the limit switch Switch closingoperations, to permit a carrier to pass from one track section to abranch section, are controlled primarily by the relay. SRS

forming part of each siding switch controller. Each such relay SRS iselectrically connected between the two control bus bar sections C3 andC5, in series with acontrol capacitor; C's. In the embodiment now beingdescribed, the relays SRS and associated capacitors CS form parts ofselective control circuits which are electrically. connected to acarrier mounted source of power, represented as a controltransformer CT,as seen in Fig. 5B, as the carrier approaches the corresponding sidingswitch. The'thus completed selective control circuits contain impedanceelements, the magnitudes whereof are variably determined in accordancewith the destination selected, and the relation is such that as acarrier approaches a siding switch, which is required to be actuated, inorder to .enable the carrier to reach the selected destination, the thuscompleted control circuit approaches resonance to the control frequency.The individual relays SRS are proportioned to be actuated in response tothe value of current which ows in such control circuits under thejust-mentioned approximately resonant conditions, and the consequentoperation of the correspondingrelay SRS actuates the switch, all as isdescribed in more detail below.

Each destination on thesystem may be and preferably is provided withcontrol apparatus comprising a selectively responsive relay SRD, andacompanion relay PGD. Each relaySRD is connected across sections CII andC|2 of the control bus bar, in series with a destination capacitor CD.Accordingly, as in thecase of the selectively operable siding relaysSRS, the destination relays SRD are operably responsive only to theapproach of a carrier which is eiective to complete an approximatelyresonant circuit,` including the relay SRD. The relays PGD function asdescribed below to stop the carriers and may also serve to institute `aseries of auxiliary control operations. l.

The control equipment` at each exit switch, is shown in full lines inFigure 5C, and comprises in addition to the indicated limit switchesELSIa, ELSZa, etc. a series of control-relays PCE, PBE, PFE', and POE,and a pair of reversing contactors CME and OME, associated with themotor EM which operates the exit switch.

The previously mentioned controller which is carried by` each carrier,and may be and :preferably is housed in the control box 36 (Figure 3).:comprises a starting contactor PMC- for the traction motor TM, astarting relay PGC, a pro.-r tective relay PFC, selecting nrelaysPALCand 1 pair of usual reversing contactors CMS .and i OMS, and aseries of relays PLS, PFS, PSS, and

PBC, auxiliary relays PXC and PZC, and `cam operated selecting switchesCSA and CSB, .see Fig. 5B.Y The cam operated switches CSA for'allcarriers are operable by cams A which, as shown in `Figure 1, aredistributed at various points throughout the system. Similarly theswitches CSBfor all carriers are disposed'tobe similarly operated bycams B which are distributed throughout the system. 'l

In addition to the foregoingY elements, the car-- rier mountedcontrollers each include a station selector which forms a part of theabove mentioned selective control circuits and the setting of whichdetermines whether a reso-nant circuit condition will be established asthe carrier approaches the several siding switches and destina-v tions.More particularly, and as shown, each Sta.- tion selector comprises,fundamentally, an inductance L, selectively different amounts whereofmay be selectively adapted for connection to the previously mentionedtuned circuits as the corresponding carrier approaches the varioussiding switches and destinations.

It will be appreciated that, generally speaking, a plurality ofselecting operations are involved in causing a carrier to move along thetrack system to a selected destination. In the instance illustrated byFigures 5A, 5B, and 5C, two such selecting operations are involved. Thefirst selecting operation is one which conditions the carrier. to socontrol the associated siding switch as to enable the carrier to passtherethrough on to the siding. Since such siding includes a plurality ofdestinations, the second selecting operation is one which conditions thecarrier to stopata selected one of such destinations to the exclusion ofthe other such destinations. Similarly, in dis-` patching a carrier to,for example, station 3A-l B associated with siding R3 (Figure 1), twoselecting operations may be said to be involved. In this instance theiirst selecting operation conditions the carrier to operate the sidingswitch SS` leading to siding R3. The second selecting operationconditions thecarrier to operate the siding switch leading from sidingR3 to the subordinate siding R3a.. Since such subordinate sidingcontains only one destination, the same selection which causes thecarrier to enter siding R3a may be used to cause the carrier to stopy atsuch destination. It will be appreciated that if such a subordinatesiding contained a plurality of destinations, an additional or thirdselection would be involved in determining at which of such destinationsthe carrier would be stopped. Other track .and siding arrangements mightrequire more than three selections tobe made in causing a carrier toreach a selected destination. The system of Figs. 1 through 8 providesfor two selections, whereas the system of Figs. 7 and 8 provides formore than two selections.

In accordance with the' present invention,.a-l1 manual operations neededto effect all selections necessary to vcause a carrier to reach aselected destination may be made at the same time, and they may be madeeither before the carrier is started or while it is traveling along thetrack.

Preferably and as illustrated in Figs. 3 and 5B, each carrier isprovided with a pair of dials 6|] and Atill; dial Bil serving generallyto select the siding containing the desired destination, and dial 64serving generally to make a selection between the individualdestinations associated with aparticular siding. In certain'cases as inconnection with sidings Rta, etc., asy mentioned above, dial 64 mayserve to make a siding selection aswell as .a destination selection.lFor' convenience: of d'escription, however, dial 60' isr hereinafterreferred to as a siding selector and dial 64 is hereinafter referred tovas a destination selector.

TheV dial 60 is provided with a plurality of different operativepositions, in which the control linger |24 associated therewith servesto introduce correspondingly different amounts of the inductance L intothe carrier mounted portion of 'the above described selective controlcircuit.

Generally stated, the number of suchl different operating positions ofthe dial 6B corresponds to the number of individually responsive sidingswitches. Thus, if dial 60 is turned to its position corresponding tothe siding switch leading to the siding R2 (Figure l), it introducesinto the selective control circuit sufficient of inductance L so thatwhen such selective control circuit is completed as the carrierapproaches such siding switch, a substantially resonant circuitcondition is produced. Except as hereinafter noted, however, controlcircuits which are completed as the carrier approaches switches otherthan the selected switch are substantially removed from resonance, sincethe selected amount of the inductance L does not match the controlcondensers CS located at'such other switches.

Similar comments apply to dial 64, which has "operative positionscorresponding in number to the-maximum number of destinations on any onelsiding or to the maximum number of siding switches leading from aparticular siding onto subordinate sidings. EachY setting of dial 64introduces a suflicient amount of i'nductance L into 'thecarrier-mounted selective control circuit so that as the carrierapproaches the selected destination (or subordinate siding switch) aresonant condition is produced. As the carrier approaches otherdestinations or' other subordinate siding switches, resonant conditionsare not produced.

In the embodiment of the invention now being described, thel selectingdials 60 and Mare selectively renderedv effective andr ineffective bythe above-mentioned! carrier-mounted, cam-actuated 'switches CSA andCSB, which switches respond,

respectively, to cams A and Bwhich are distribrvutedf along` thel tracksystem. Cams A are so located around thc system that the4 sidingselector ('dial' 60) is rendered effective prior to the approach of' thecarrier to any siding switch which v such carrier might needto operatein traveling fromy its starting point toa selected destination; The'cams `B are so located, in turn, that the destination selector' (dial649 is rendered elective betweenV the time the carrier enters aparticular siding and the time the-carrier approaches the selecteddestination or corresponding' subordinate siding. Locations for camsv A-and B which satisfyl thel above requirements are illus- Itra-ted inFigure 1-.

4Inmany cases-y it isy desired' to have a carrier automatically returnto a normally fixed, but

selectable, starting position (such as destination IfA-IB, Figure l)after havingl complete-d` a' tri `for the station IA-I-B.

Inl Figures A, 5B, 5C, 6; and` 8, the various relay and contacter coilsand contactsI are-shown separately from each other, solasto simplify thev drawings; Coils and contacts bear identical rciyerence characters withthe exceptionthat the -The following Relay and Con'tactor Scheduleidentiiies all contacts operated by a particular coil and indicatescertain operating characteristics thereof. Moreover, the limit switchessuch as SLS'la, etc., are indicated in Figures 5, 6I, and 8, asA being.structurally separate.. The' operating characteristics of these limitswitches are specified in Fig. 9", and it will be understood that theselimit switches may be conventionally constructed and maybevconventionally mounted upon the switch structures shown in Figurev 4.Similarly, the carrier mountedr cam switches CSA and CSB may be normallyopen', momentary contact, switches', adapted to be closed only whileengaged by the correspondingl cams A and B.

Relay and contactar schedule Relay or Contacter Normally Closed In theabove schedule, relay PFC is low in. im'- pedance; (for-example,50001-ohm`s whereas helays PLS, PLS", PCE, POE, PBE'an-d PSS arehigh invimpedance @for example, 50,000 ohms); Any of the last mentioned relayswill operate:` when connected inl series with relay PFC" across thebuses X--Y, whereas, undersuch conditions-relay PFC will' not operate;since' it requires substantially full-.X-f-Yfvoltage' to operate it.Relays SRS, SRS and SRD have' the responsey characteristics 'describedbelow inconnection with the tuned' circuits, and theA other relaysvandfcontactors in thel schedule may be ordinarily rated devices designedto require i substantially full X--Y vol-tage to operatethem'.

It is believed that the' remaining details of the present embodiment maybest be understood with reference to descriptions of typical operatingsequences, it being recalled that all relays and contactors are shown inFigures 5A, 5B, and 5C in the normal cle-energized positions thereof,that the limit switches are illustrated inV the positions that theyoccupy when the correspondingv track switches are in the illustratedopen positions, and that the carrier mounted cam actuated' switches arelillustrated in their normal open positions. Under such conditions, anynumber of carriers may be considered as being located at random aroundthe system, with their power and control collectors in electricalengagement with the power and control buses X, Y, and C.

As an example, the carrier, the controller for which is shown in Figure5B-andas being located at destination 2A-|B, may be considered asinitially located at the destination IA-IB- in'Figyure l, in whicheventl its power and control collectors occupy the same relativepositions, with `rier. gized until a selected destination is reached,and

ience, the operations involved in starting a carrecalled that the returnbus Y is continuous throughout the system and that the power bus X iscontinuous except that it is sectionalized at each destination, todefine a` short section XI. Portions of the bus bar X at either side ofeach short section XI are continuously interconnected by jumpers |08.Under the present conditions, the section Xl at the starting point isconnected to the adjacent sections through the now closed back contactsPGDb of the control relay PGD, appearing in Fig. B.

Closure of contact PGCd completes a circuit through the tractor motorstarting contactor PMC, which thereupon closes contact PMC'a, startingthe tractor motor TM. Closure of contact PGCd alsocompletes a circuitfor the primary winding of the control transformer CT, therebyenergizing the latter. This `action is preparatory only, since thesecondary lcircuit of this transformer is interrupted at contacts PALCaand PBCa of the lselector relays.

Closure of contacts PGCb and PGCd of the `starting relay PGC'electrically connects the leading control collector LC to the powercollector 40 associated with the power bus X, through a circuit whichextends from collector LC through `contacts PGCb, the coil of the'protective relay PFC, contact PGCd, and collector 40 to the power bus X.Under the conditions stated, no circuit `to the return conductor Y iscompleted through (control collector LC and consequently no currentflows in the just traced LC`40 circuit. Completion thereof does,however, elevate collector LC to the potential of the power bus X.

It will be noticed that the circuit for the starting relay PGC willremain complete so long as .the carrier mounted supply conductors |04and |06 are energized, but that the circuit-for the tractor motorstarting contactor PMC is additionally subject to the back contacts PFCbof the protective control relay PFC. The last-mentioned `relay remainsdeenergized unless and until, as

described below, the associated carrier approaches a track switch whichis under control of a leading carrier or is otherwise not in shape toreceive the carrier in question, or unless such carrier approaches tooclosely to a stalled leading car- Conductors |04 and |06 are notde-enerconsequently the operations described above serve to place thecarrier in operation and to maintain it in operation until a selecteddestination is reached.

As to the selection of the destination, selecting dials 60 and 64 areshown in Figure 5B, in positions corresponding to the destinationZA--IBSuch setting is preparatory only, since the associated circuits areinterrupted at kthe now open contacts PALCa and PBCa of the selectingrelays. As the carrier in question approaches the exit switch ES at theexit end of the siding RI, the

switch is automatically closed thereby so as to permit the passage ofthe carrier in question on to the main line R. The operations involvedare the same as those involved in moving a carrier from the sidingshownin. FiguresA, 5B, and 5C on to the main line and consequently maybe described with reference to Figure 5C. More particularly, as thecarrier in question approaches the switch ES, the control collector LCmoves into engagement with the control bus section C20, which sectionis'directly connected,

through conductor |0, andthe coil of the switch closing relay PCE, -tothereturn power busY. Under the conditions stated, collector LC is atthe potential of, and is electrically connected to, bus X. This action,therefore, completes a circuit for relay PCE, through the previouslytraced circuit between the control collector LC and the power collector40, in response to `which relay PCE assumes the energized position,opening its contactsv PCEa and closing its contacts PCEb. The operationof contacts PCEa is without effect in connection with the operation `nowbeing described (being concerned with preventing interference betweencarriers), but closure of contactsv PCEb completes an obviousenergizingcircuit for the coil of the switch closing contactor CME,which thereupon closes its contact CMEa and energizes the switch motorEM, causing thelatter to move the switch ES to the closed position.

It will be noticed that in the just described circuit for the switchclosing relay PCE, this relay and the carrier mounted protective relayPFC are in series relation. As is pointed out above, relay PCE isrelatively high in impedance compared to relay PFC. Consequently, lwhensuch relays are energized in series, the voltage drop across relay PFCis insufficient to operate the latter, whereas the voltage dropr acrossrelay PCE is sufcient to operate it.

When the switch ES reaches the fully closed position, limit switch ELSZaopens and limit switch ELSZZ) closes. Accordingly, when the controlcollector LC passes out of engagement withbus barsection C20 and intoengagement with section C2i, the circuit for relay PCE is maintainedthrough limit switch ELSZb. Under such conditions, accordingly,- thecarrier is enabled to pass into the switch.

On the other hand, if the switch-ES has not reached the fully closedposition, by the time collector LC passes out of engagement with sectionC20, the carrier is automatically stopped at the entrance to the switch,until such time as the switch does attain the fully closed position.More particularly, under such circumstances, when the control collectorLC moves into engagement with section C2 I, the still closed limitswitch ELSZa directly connects the control collector LC to the returnconductor Y, thereby impressing full X--Y bus bar voltage across theprotective relay PFC. Relay PFC is operably responsive to such bus barvoltage and thereupon assumes the energized position, closing itscontact PFCa and opening its contact PFCb. Contact PFCa isconcerned withthe stopping of a following carrier, described hereinafter, but theopening of contact PFCb interrupts the originally traced circuit for thetractor motor contactor PMC, which thereanoniem upon opens,de-ene`rgizingr the tractorH motor." TM, and stopping the carrier. Assoon as the switch ES. does. reach. the fully closed position limitswitch ELSZa opens, disconnecting section C2i and consequently theAcontrolv collector LC, from the return bus- Y.'. This de-energizes theprotectve:- relay' PFC., and restores the circuit. for tractor motorcontactorPMC, enabling the latter t'o close its contact PliC'c' and'restart the associated carrier;r

It will be noted that when the track. switch rreaches the closedposition, the consequent open@ ing of limit switch ELSZc dez-energizescontacter "CME and stopsi the switclfimotorl EM.

When the leading collectorrLC passes. out. of

engagement with section C2i, allenergizing circuits for relay PCE areinterrupted andA the latter resumesl its illustrated. position',reclosing its. contacts PCEa and 'iGEc and reopening its Contactl PCEbiThe rec'losureof ContactA PGE@ is;l Without. effect in the sequence newbeing, described: 'l'hereopening of contactPC'Eb islwith.- out` effectsince limit switch- ELSZc is: nowopen, and the reclosure ofi. contactPCEc servesl only to prepa-rethe switch, closingl circuits.y

The-control section CIJ is atleast aslong as, and'. is preferablysomewhat longer than, the 'spacing between' the: controly collectors LCand TG.. Consequently, thezleadingt collectorLC does not; engage thecontrol sectionV Cl8 until. the carrierhas. fully cleared the Switchs.When. sectionv (3l-8v is.- so engaged, an; obvious circuit, throughythenow closed contactsfl?CEc, is-com pleted for the switch opening relayPOE, which circuit.- includes the. high impedance relay POE and the.carrierl mounted protective. relay PFC inseries. relation- As in thecasev ci, relay.v PCE, .relay PFCI fails to. operate; but relay PQE:l isenergized, and closes'. its sole contact POEw, thereby energizing theopening contacter OMEa for the switchmotor EM. VAswillbeobvious, thisaction causes` contact OMEav to close, andenergizes the switch. motor EMin a direction to cause the. switch to move to the open position. As theswitch starts away from the closed posinon., the 11min` switches Etsen.Ensae, and

ELSZc resumel the illustrated positions.. and, when the switch reachesthe fully open:- position, the limit switchesA ELS.I.a,.. ELSllaandELSIc .resume the illustrated. positions.` The opening 0f.' limit switchELSIc,l of course;` deeenergizes theswitch motor.`

As the leading control collector LCL leaves secf tion C18., the circuit.for the opening relay POE interrupted; thus restoring alll of.. the exitswitch circuits to.. the illustrated. condition.V y

Asispointed out. above, inthe illustrated em.- bodiinent, theselectionsl made-v by the Acarrier mounted? dials.- 6D". and B2.-determine the. points. at which the associated'A carrier shall4 leavethemain line and turn on t'o a siding.. Accordingly, in sucliillustrated'. embodiment, the cams.. A1 (Eig..- ure 1)` are locatedaround. the system in`l such positions that,.bet'ween. the time a.carrier leaves a sidingz and'. the. time it. reaches. another sidingswitch,` the A or switch. selecting circuits are rendered. effective.Thus as appears in. Figure 1`, acam A is positionedbetween the. switchat the. exit. endy of thev siding, RI, and the siding switch leading ontothe siding R2'.4 As the cary.

rier passes. thej ust-mentionedcam Authe carriermounteL,cam-operatediswitch. CSA. ismomentarily closed,v which action completesyan obvious energizing circuit for. the. selecting: relay PALG.

When soA energized relayl closes its-` sole cmrtazct FALC and. being; ofe latching type, pnovidedl with: ai. usualila'tch, |204; it latches:itself in'. closed; positiom. `Aa the carrier leaves canr. A\accordingly. the' reopening of. cani-.switch GSAv is: without efiect..

tf'ilosur'el ofrcontaci PALQa electrical-lyI connects the'two control:collectors; LC.y and 'I-C together through. a; circuit. whichi. extendsfrom collector LC through they now closed contact E'Grtilb,vr thesecondary' winding CT ofy the controlr transformer,` ai small:protective'v resistor |22;l aportion of thefinductance1;.,l movable:tapi243. now' closed back contact PZCc, andy theH nowL closedl frontcontact- PALCc to thetrailing collector TG; In response?l to: completionoi.A the: just-mentioned circuitt a# potential differenceequal toft-heoutput voltagev of control transformer CT is. impressedbetweenthecollectors LC andf TC., If under the conditions stated, bothcollectors and TC shouldl engage.l the control. bus C, transformer CTwould.I be.- enabled tofpass current through the just` traced LC..r and;FO circuits.. Such a.. circuilating currentlwoulct befof no consequence,since such circuit includes no relay or contactor coils and moreover,such` current would. be or a comparatively7 lowf values in view of lthey presence` in the? circuit ofr at; least. a. portion of theimpedance Land' resistor. |22; Since the sections Cl ot the controlbusare shorter'than the'spacingbetween the collectors, the just.mentioned circulating current is enabled. toy iiow only during intervalswhile. the carrier is passing.,l over sections; such as CIL., which. arelonger than the and. 'IIC' spacing.

As` the carrierapproaches.v the siding. switch -SS. leading on' to. thesiding R2. (Figures lA and ,5A),.the. leading. control collector. LCpassesinto engagement; with. the initialswitch. portion C.| of theAcontrol bus. If., atthe. time controlV collector LC engages sectionACI', thev switch SS isr in its normalopen condition,.such engagement iswithout eect.. and theY carrier movement. continues uninterruptedly.. Itatsuchtime theswtch SS is in any position other than the. fully openposition, the. limit switch. SLS l c is. closed. and. is consequentlyeffective to directly connect the section. C Il and consequently the.leading` collector LC; toy thefreturn bus Y.. It will be recalled thatatlemyv time that. the collector LC is. directly connected'. to thereturn bus Y,'. the protective relay' PFC'i's.- energized,` and.operates tostop the carrier;l As soon as limit. switch SLSIcopens,however', indicating that. the switch SS` in normal condition, thecarrier mounted protectiv'erelay PFC' is de-enei'gize'd, enabling the.car- 'ri'e'r tore-start. Y

Engagement of control bus sectionlCZ is with.- ouyt. eiect'. So, also,is engagement oi section C3- ey'- theleading conector' Lc. shortly aftertlf'ie' trailing collector 'IC leaves section Cl, the leading collector'LC engagesA section Cl.

Engagement of C4 by collector LC. may or maynot have any effect upon themovement of theJ carrier in` question: If" the: siding switch 'SS in thefully' openv position, limit switches SLS'IQJE andr SMS2-15` occupyither illustrated positions',y and: so'. do notv complete anydirectoircuit: between section GAL and; the return4 bus Y.. VUnder suchconditions;A such engagement completes a circuit fromv `collectorthrough coilofv high impedance relailv PSSv and limit switch: SLSZU to.the: return bus Y. It will be recalled,l however, tha-t a direct orvirtually direct connection. between collector LC and the I return bus Yis neededin. orderl tof operatethe `,all other siding switches.

`form to the' following schedule.

carrierl'mounted protectivev relay.l PFC. Consequently, thejust-mentioned circuit including relay PSS does not complete 'an.operation of the protectiverelay PFC and-the carrier movementcontinues. Completion of such circuit does, however,- energize the highvimpedance relay PSS which thereupon closes its-contact PSSa. Thisconnects section Cl to the return bus Y, in readiness to stop anyfollowing carrier'. f

On the other hand, if, at the time section C4 isengaged by'collector LC,the switch SS is in some intermediate position (indicating an abnormalcondition),` both limit switches SLSIb and SLSZb are closed, whichaction causes an operation of thev carrier mounted .protective relayPFC, causing the carrier tostop until the faulty condition is corrected.

As the leadingr collector LC passes the section C4', the collectors LCand TC move into engagement, respectively, with the spaced sections C5and C3 ,thereby completing an output circuit for the "controltransformer CT, having predetermined components of inductive andcapacitive reactance More particularly, such circuit extends from onesecondary terminal of transformer CT, through resistor l22,a portion ofinductance L determined by the setting of dial 60, the trailingcollector TC, bus bar section C3, capacitor CS, the coil of the'selective relay SRS, section C5, the returning control' collector LC,and contact PGCb to the other secondary terminal of transformer CT.' Insuchcircu'it al1 of the capacitive reactance', for practical purposes,is represented by condenser CS, and the inductive reactance is, ofcourse, represented primarily by the inductance L and relay SRS. Theimpedances of transformer CT and relaySRS may he regarded ascomparatively lowA and preferably the resistive components of thecircuit are low in relation to thereactive components. Thus, theresonance curve of the just traced circuit is relatively sharply peaked.Similar comments apply to the tuned circuits for other siding switchesand for the destinations. Consequently, if the reactance represented bycondenser CS is approximately equal to the inductive reactance of thecircuit at the frequency of the alternating voltage energizing thesystem being described, transformer CT is enabled to pass a relativelyhigh current through the circuit of a value sufficient to operate theselective relay SRS.` It will be apprecir ated, accordingly, that thecondenser CS, at the siding switch in question, is proportioned toinatch the setting of dial 60. Similar comments apply to the condenserswhich are associated with That is to say, the condensers at the othersiding switches are proportioned to match the corresponding amounts ofinductance Lk which are included in the tuned circuits at thecorresponding different settings of In an illustrative case, andassuming 60 cycle alternating current and that the reactive com- `CS andCD and by the included portions of inductance L, the condensers and theincluded porl-tions of inductance L for various A and B settings ofdials El) and 62 and 64 and 66 may con- Greater or smaller differencesbetween successiver capacitive and inductive values may, of course, beemployed if desired, depending upon the sensitivity of the relays suchas SRS and SRD.

Approximate L and CSk o'r CD values resonant at 60 cycles Portion of Lin circuit CS or CD at Siding or Desti- Included portions nation correofReactance of sponding to dial L, CS or CD Position of Dials Henriessetting'- (Ohms) (microfarads) .185 38 70 370 18. 7 140 555 12. 6 210740 9. 4 280 .925 7. 5' 350 l. 110 6.3 420 1. 295 l 5. 4 y49o 1. 480 4.7 560 l. 665 4. 2 630 1. 85o 3. s 70D Reverting now to the controloperation in progress, the selective relay SRS-upon being operated,opens its contact SRSa (Without immediate effect) and closes its contactSRSIJ, thereby completing an obvious circuit for the closing contactorCMS associated with the siding switch mo#- tor SM. This action causesclosure of the contact CMSa and starts the closing operationof theswitch SS. As soon as the switch SS reaches the fully closed position,limit switch SDSZa opens, de-energizing the siding switch motor.

As soon as the siding switch SS 'starts towards the closed position,t'he previously identified limit switch SLSIc closes, completing adirect connection between section Cl and the returnbusY, for thepreviously identified Acontrol of any following carrier. Y

It will be noticed that between the time the leading control collectorLC left section C4 and the limit switch SLSIc closed, the circuit forthe coil of relay PSS is interrupted. As indicated by the legend,however, relay PSS is of a usual slow lreturn type, and is effective tomaintain itscontact PSSa closed sufliciently long' to maintain theconnection for section Cl until such a ytime .as the limit switch SLSIcdoes close. The just'- mentioned timing interval is, of course, veryshort.

When the control collectors LCA and TCjpass outof engagement with thesections C3 and C5, they previously identified tuned circuit isinterrupted, thereby de-energizing relay SRS, which actionv is Withoutimmediate effect since the cir-A cuits controlled thereby areinterrupted' else# where. As it leaves section C5, the leading controlcollector LC engages section C6. Assuming that the track switch is nowfully closed, such engagement is without effect injview of theopencondition of limit switch SLS2b. If the switch is not fully closed, suchengagement immediately connects collector LC to the return 'bus' Ythrough the now closed limit switchesv SLSIb and SLS2Z2, therebystopping the carrier.

Assuming the switch is in proper condition, th carrier passes on to thesiding R2, and collector LC passes across section C9 without effect andengages section CIU. 'This action completes'an energizing circuit forthe closingof relay: PLS. This circuit includes relay PLS and thecarriermountedprotective relay PFC in series, butfas before, due to therelatively high impedance of relay PLS, relay PFC does not operate.Relay PLS does operate, however, and closes its sole contact PLSa,completing a circuit through the now closed limit switch SLSia, for theswitch motor opening contactor OMS. Upon being energized, contactor OMScloses its contact OMSa. energizing the motor SMand causingthelatter toaccenni return the Switch SS to the illustrated Open p0- sition. As soonas the switch moves away from the closed position, the limit switchesSL52@ and SLSZb resume the illustrated positions, and as soon as theswitch attains the 4fully open position, the limit switches SLSIa, SLSIb, and SLSlc resume the illustrated open positions, thereby d@-energizing the switch motor SM and disconnecting the control section Cifrom the return bus Y. The latter is without effect vexcept in the eventthat a following carrier has its leading control collector in engagementwith the section C I.

At any time after completing its movement through the switch SS, thevcarrier may encounter a cam B, thereby transferring the control of thecarrier from the yswitch selecting elements to the Destination selectingelements. As shown in Figure 5A, a cam B is located in the immediateregion of the control section CII). Upon being engaged, this 4cam closesthe carrier-mounted cam-operated switch CSB, which, at its contacts a,energizes the reset winding Ist associated with the A selecting relayPALC. ,at its contacts b the switch CSB completes an obvious energizingcircuit for the B selecting relay PBC which thereupon assumes theenergieed position, closing its contacts PBCa and PB Cb. At the lattercontacts, relay PBC completes a self-holding circuit for itself and atthe former contacts, relay PBC renders the dial 54 effective todetermine the amount or" inductance L which is included the selectingcircuit which extends between the control collectors LC and TC. 1t will'he noticed that the opening of the A selecting relay PALC renders dialsc@ and e2 ineffective. lIn Fig. 5B, dial Eid is in a positioncorresponding to the rst station IB and it will he understood that thecontrol condenser CD in the control circuit for the indicateddestination ZA-l B is proportioned to match the just-mentioned settingof the dial 54.

Accordingly, when. the carrier reaches the position shown in Figure 5B,in which collectors LC and TC' are in engagement, respectively, with bussections CE l and CE2, a circuit including vthe destination selectingrelay SRD is completed, which circuit extends from the coil of relaySRD, section CII, collector LC, contact PGOU, the secondary winding ofcontrol transformer' CT, resistor |22, the portion of inductance L whichis determined by the setting of dial 54, and thence through contactsPZCa and PBCa, collector TC, section C i 2, and condenser CD to theother terminal of coil SRD. Since destination ZA-IB corresponds to theindicated setting of dial 64, the reactive components of said circuitare substantially balanced so that the circuit is in a substantiallyresonant condition. Consequently, a relatively high current flowstherethrough land operates relay SRD, which thereupon opens its contactSRDc and closes its contact SRDb. Closure oi contact SRDb energizes thestopping relay PGD, which thereupon closes its contact PGDa and opensits contact PGDb. The opening of the latter contact isolates the sectionXI or the power bus X, which as will be understood, has the effect ofcle-energizing the carrier-mounted con.- trol conductors l te and -I tt.The last-mentioned action automatically de-energizes the tractor motorTM, the carrier starting relay PGC, the B selecting relay PBC, thetractor @motor contactor PMC, and the control transformer CT, therebyrestoring all carrier-mounted circuits in Fig. 5B to the conditionshown. The cle-energization of the tractor motor TM, of course, bringsthe care rier to rest at the `destination 2A|B.

0 3f the just mentioned transfer switch TS may lhe Assuming that therltransfer switch TS in series with contacts PGD@ and SRDa, is in theopen position, the alcove operations which result from thede-energization of conductors IGA and |06 are `all that take place as anincident to the stopping of the carrier at the vdestination 2A|B. ltwill be understood that under such circumstances the carrier may herestarted from the just mentioned destination by again closing thestarting switch |06, therebyduplicating the previously describedoperations, and it will be appreciated also that either before or afterthe restarting of the carrier, a new destination selection may be madeby appropriately setting the dials til and 64 to correspond to thedestination selected. In many cases, however, it may be desired toautomatically perform other operations as an incident of the stopping ofthe carrier at the selected destination. For example, the

carrier may be suspended from the tractor by means of hoistingapparatus, dumping apparatus, or the like, and it may be desired toactuate such hoisting apparatus, dumping apparatus, or the like upon thearrival of the carrier at the selected destination. Additionally, it maybe desired to automatically select a predetermined return destination,such, for example, as the original starting point |A- IB, to which thecarrier shall return as soon as it is started. Tor accommodate suchoperations, as well as others,

moved to the illustrated closed position. In such event, thede-energization of selecting relay SRD which takes place when thecontrol transformer CT is tie-energized, as aforesaid, causes relay SRDto resume the dse-,energized position, interrupting the circuit forrelay PGD at contacts SRDD.y Relay PGD is of the slow return type,

and, consequently, it maintains its contact PGDa closed for a `shortinterval after the circuit for the coil is interrupted. During thisinterval, both of contacts PGD@ and SRDa are closed, and complete acircuit for the auxiliary control relay PXC, which circuit extends fromthe power bus X, through transfer `switch TS, contacts PGDa l and SRDa,control section CII, collector LC, the

coil o f relay PXC, and the now closed contact PGC'c and collector 42 tothe return bus Y. Upon completion of this circuit, which remainscompleted only momentarily, relay PXC is energized and closes itscontacts PXC@ and PXCb. The operations resulting from closure ofcontacts PXCb are not illustrated,' sinoe they form no part of thepresent invention. They may he, for example, dumping, hoistingoperations, or the like,

` which operations conventionally may be instituted by momentary closureof contact PXCb. At its .contact PXCIL relay PXC prepares an enerelainecircuit .for relay PZC- At the expiration of the short timing intervalof relay PGD, it reopens itscontact PG-Da and recloses its contact PGDb. The latter action reenergizes bus section XI. The opening ofcontact PGDa interrupts the energizing circuit for relay PXC. Relay PXCis of theslow return f type, and consequently its contacts PXCc remainclosed for a short interval after bus XI is reenergized. During thisinterval relay PZC is enerized through an obvious circuit, andimmediately completes a selfholding circuit for itself through contact PZCe, enabling relay PXC to time out without effect. As will be evident,the holding circuit for relay P ZC remains complete until the controlconductors IM and itt are again cie-energized 4by the arrival of a carat a selected destination. At its contacts PZCd, PZCd,

19 PZCc, and PZCd, relay PZC disconnects dials G and 64, land connectsdials 62 and 56, which may, of course, be set to correspond to anydesired destination on the system. As shown, dials 62' and 66 are setfor the initial starting point lA-iB and it is believed to be obviousthat if the carrier be started, by re-energizing the starting relay, thecarrier will travel along siding R2, operate the exit switch ES at theexit end of such siding in the manner previously described and reenterthe main line R. In traveling along the siding R2, the carrier will passdestinations 2A-2B through ZA-IBB thereon. In successively passing thesedestinations, the tuned circuits of the present invention will besuccessively completed. In each instance, however, the values of thecapacitor CD at the various destinations will be such that resonantconditions will not obtain and, consequently, the selective stoppingrelays SRD`wil1 not be energized. In the absence of such energization,no stopping action occurs, as will be understood.

As appears in Figure 1, an A cam is encountered shortly after thecarrier in question leaves siding R2 and re-enters the main line, whichaction, as before, energizes the selecting relay PALC, rendering thedial E2 effective. It will be appreciated the siding switch SS at theentering end of the first siding RI is provided with a selectingcondenser CS which matches the first tap on inductance L. Consequently,with the indicated setting of dial 62, the carrier will operate thesiding switch SS in the manner described in connection with the sidingswitch shown in Figure 5A, and will re-enter the siding RI. Afterentering such siding Ri, a B cam is encountered, transferring thecontrol to dial 66. It will be understood that the destination controlcircuit for the station lA-IB, includes a control condenser CD whichmatches the rst tap associated with'dial 66. Consequently, upon reachingthe destination lA-IB, the carrier is stopped in the manner described inconnection with the destination 2A-IB.

It will be recognized that usually the transfer l switch TS in thedestination control circuit for which dials S2 and 66 are set, will beopened since no automatic station selection or other automaticoperations will be desired as a consequence of the arrival of thecarrier at the starting point.

Also, the carrier mounted transfer switches lill, |03, and |05 enablethe automatic dumping (or other), redispatching and restarting functionstov be selectively provided or omitted.

It will be appreciated that the re-starting of the car from adestination to which it has been dispatched may be effected eithermanually, by closure of the starting button it, or automatically bymomentary closure of the parallel connected contacts Mt, which may beoperated in any automatic manner as a consequence of they completion ofany automatic dumping, hoisting, or other operations which have takenplace at the destination as a consequence, for example,

of the closure of contacts PXCb.

Reverting to Figure 1, it will be noticed that all of the destinationsZA-IB through ZA-IB are disposed along the same siding R2. In beingdirected to a station on siding R2, 'the A selection (carrier-mounteddial t0) serves only to control the operation of the entering sidingswitch, and the B selection (carrier-mounted dial 64) serves only toselect the particular destination along the siding at which the carrieris to be stopped.

sented by sidings R3 and R4, and the interconnecting subordinatesidings, it will be noted that, in traveling from any point on the mainline to any of the destinations, such as destination 3A IB, two sidingswitches are required to be operated, one being the siding switch SS atthe entering end of the siding R3, and the other being the siding switchSS at the entering end of the subsiding R3a which contains thedestination 3A- lB. The former switch SS, at the entering end of thesiding R3, being common to all of the destinations SA-IB through3ft-16B, is operated in response to an A selection, as in the previousexample. The switch SS at the entering end of the sub-siding, however,being individual to a particular destination, is operated in response tocompletion of the resonant circuit which is prepared by the setting ofthe B selecting dial 64. Accordingly, the B cam associated with sidingR3 is located in advance of the sub-siding containing the destination:iA-EB. Thus, the B selection serves to control the operation of suchswitch SS, in the manner described above with reference to Fig. 5A; andalso serves to control the stopping of the carrier (and any automaticoperations incident thereto) at the station 3A-|B, in the mannerdescribed with reference to Fig. 5A. Accordingly, the control condenserCD for destination SA--IB and the control condenser CS for thecorresponding sub-siding switch SS have substantially the same capacity,so that the IB setting of dial 6ft is effective to complete, inconjunction therewith, resonant circuits for the corresponding relaysSRS and SRD. Similar comments apply to the destinations 5A-IB, etc.,which occupy the sub-sidings between sidings R5 and R6.

Considering now the arrangements for preventing interference betweensuccessive carriers traveling along a main line or a siding, and forpreventing entry of a carrier into a siding which is not in shape toreceive it, it will be recalled that having been started, as by closureof its associated starting switch lili), a particular carrier remains inmotion until such a time 'as it is stopped in normal fashion by itsarrival at a selected destination (resulting in the de-energization ofthe carrier mounted control conductors H04 and |06) or until it iscaused to make an emergency or protective stop in response to theenergization of its carrier mounted protective relay PFC.characteristics of relay PFC are such that this relay will respond onlyif it is subjected to substantially' full X-Y bus bar voltage; and thatan eifective energizing connection for relay PFC is made whenever itsleading control collector LC encounters a control bus bar section whichis directly connected to the return bus Y.

Reverting to Figure 5A, it will be recalled that as soon as the leadingcontrol collector LC of a leading carrier has engaged the controlsection C4 (and assuming the switch SS is in its normal open positon) anenergizing circuit for the coil of relay PSS is completed, whichthereupon becomes effective, by closure of its contacts PSSa, todirectly connect section Cl to the return bus Y. If under theseconditions a following carrier reaches the section CI, the circuit,indicated in dotted lines, near the bottom of Fig. 5A, for itsprotective relay PFC, is completed, and such following carrier is causedto stop and remain at rest until the connection of section CI to thereturn bus Y is cleared. Ifthe leading carrier It will further berecalled that the is en route to a destination which requires that itshall close the switch SS of Figure A, it iS effective to operate therelay SRS, thereby actuating the switch as previously described. Suchactuation closes the limit switch SLSIC, which thereupon maintains the Ybus connection to section Cl, until the leading carrier has passedthrough the switch and the latter has been automatically reopened.

If the leading carrier is not prepared to operate the switch SS at thesiding switch in question, it does not operate the relay SRS. In thisevent the circuit for relay PSS is interrupted while collector LC of theleading carrier is passing over section C5 and engages section C6. Thisoperation, of course, requires only a comparatively short time, lessthan the timing out period of relay PSS. As soon asthe control collectorLC of the leading carrier engages Section C6, the circuit for relay PSSis recompleted, through the now closed limit switch SLSZb. This circuitfor relay PSS is maintained by the leading control collector LC until itpasses out of engagement with the control section C1. Before collectorLC leaves section C'l, the latter is engaged by the trailing collectorTC, which maintains the holding connection for section CI until theleading carrier has cleared the switch SS.

More particularly, it will be noticed that under the conditions stated,the trailing collector TC is electrically connected to the power bus Xthrough a circuit (Figure 5B) which includes now closed selecting relaycontacts PALCa, one or the other of contacts PZCC and PZCd, one or theother of brushes |24 and |25 (depending upon whether the carrier is, atthe time, proceeding under the control of dial B or dial 62), a portionof inductance L, resistor |22, the secondary winding of controltransformer CT, the coil of protective relay PFC, and now closedcontacts PGCd and collector All to the power bus X. All of the relayswhich are designated in the foregoing relay and contacter schedule asbeing high in impedance, are suinciently high in impedance, compared tothe total impedance of inductance L and any other impedance elements inthe just-traced circuit for collector TC, to be operably responsive, andto prevent an operation of relay PFC. Consequently, when collector TCengages section CB (Figure 5A), it completes an operating circuit whichmaintains relay PSS in 'the energized position. As will be evident, thisenergizing circuit is maintained until the leading carrier completelyclears the switch, at which time the trailing co1- lector TC thereforpasses out of engagement with section Cl. This action de-energizes relayPSS and restores the switch circuits to the illustrated conditions,enabling the following car to automatically restart.

From the foregoing it will be seen that if a following car is enabled topass section .CI of the control collector (Figure 5A), it means that anycarriers ahead of it have entirely cleared the switch. If such followingcarrier is under way to a destination which does not require anoperation of such switch it is consequently enabled,

upon restarting, to pass the switch without effecting an operationthereof. On the other hand, if such following carrier is under way to adestination on the siding to which suchswitch leads, such carrier should4not be enabled to close the switch and enter such siding unless vthelatter is in -condition to receive it. If the siding is not in conditionto receive 'the following carrier, ythe latter should be caused `toby-pass `the siding, and

proceed along the main line, so .as not to obstruct the progress of anyother following car.- riers.

As an example, it may be assumed that the carrier shown in Figure 5B haspassed through the switch SS and has come to rest at :the indi` catedposition, with its trail-ing collector TC in engagement with the.control Section CIZ. When such leading or rst carrier cleared'seoton YCand engaged section C10., it reopened the switch, in accordance withprevious description, en abling any previously held following or secondcarrier to restart. Such following or second carrier, if destined forthe siding in question, `causes closure of the switch, and passestherethrough, ultimately atta-ming the Ldotted :line position shown inthe upper right-hand portion of Fig.- ure 5A. In reaching such position,it operates relay RLS, at section Cim, reopening the switch. When theleading collector LC' of v,such Second carrier engages the section C12.,.its protective relay PFC is energized through .a circuit which extendsfrom the power bus through the collector 40 of such second carrier,associated contacts PGCd, the coil of its relay PFC, Vassociatedcontacts PGCb, and its collector LC to the control section Cli2. Underthe conditions stated, such control section ,is `directly `connected tovthe return bus Y through the trailing .collector of the now stoppedleading carrier (Figure 5B).

This return .circuit extends .from `the trailingr collector TC of suchleading `collector through the now closed contact PGCa, and its returnbus Y. Upon .completion kof this circuit the protective relay PFC forsuch secondfcarrier assumes the energized position, `and stops Suchcarrier in @C- cordance with previous description. Upon being stopped,the trailing collector TC of such second carrier connects the thenengaged control bus section vC9 directly to return, through a circuitlike that just .traced :for the trailing 6.01- lector TC of the leadingcarrier. Upon completion of this circuit, the relay PFS (Figure 5A) isenergized through an obvious circuit extending between control buses Xand and thereupon assumes the energized position, opening its solecontact PFSa. When open, contact PFSa prevents completion of a circuitfor the closing contactor CMS associated with the switch motor SM.

As soon as suchsecond `carrier engaged control bus section C10 andreopened the switch, any other following or third carrier (such as theone' indicated in dotted lines at the 'bottom of Figure 5A) is enabledto start. If such third carrier is not destined for the siding inquestion, it passes the switch without interference, as will be obvious.If such third carrier is destined for the siding in question, itis.ineffective to reclose the switch, because of the now .open'condition ofrelay contacts PFSa. Such third vcarrier is consequently caused to passthe switch without operating the same. 'It is believed to be obviousthat lsuch third carrier is caused to travel upon the main line, withthe system of Figure 1 as thus far described, until it has completelyrounded the main line and again approached the siding in question.During such trip, such third carrier ley-passes any siding switches SSwhich it encounters, because its dispatch setting does not match therswitch controlling `condensers at such other siding switches.

It will be recognized, accordingly, that so long as the trailingcollector of thesecond carrier .eng gages the section C9, it preventsany such ythird carrier from entering the siding in question. As

